The present invention relates to electronic keys, and particularly to electronic keys which can interface readily to a personal computer.
An electronic key is a circuit which performs the function of a key, using stored information instead of shaped metal In order to fulfill this function, an electronic key should preferably provide two kinds of concealment: the data in the key's secure memory should be concealed, and the password which permits access to the key's secure memory should also be concealed.
Electronic keys are used primarily to provide access to secure electronic data upon receipt of a valid password and to prohibit such access if an invalid password is received. One such application is the use of an electronic key hardware module in conjunction with commercially available software. The electronic key module is attached to the computer operating the software in a manner to allow the software to access the electronic key, and the software is programmed with an algorithm to verify that the module is attached to the computer. Thus, while the software is easily copied, the electronic key hardware module is not; and the software cannot, therefore, be simultaneously used in several computers.
An electronic key may have to withstand harsh environments (such as users' pockets), and is therefore normally housed in a compact package with a high degree of physical robustness.
This creates some difficulty in software copy-protection applications: how is the electronic key to be connected to the end-user's computer? Many accessories (such as mouses, modem, and joysticks) use the two serial ports of a standard PC, and therefore it is not practical to take over a serial port. If an electronic key adapter could be inserted into the standard printer port, this would be most advantageous; but there are hidden difficulties in implementing this, as will now be described.
The 1985-1986 Product Data Book of Dallas Semiconductor, which is hereby incorporated by reference, contained preliminary descriptions of a DS1201 Electronic Tag, a DS1204 Electronic Key, and a DS1250 Electronic keyring. The DS1204 was an important early development in electronic keys, and required 5 connections (for a 3-wire serial interface, plus power and ground). The DS1250, as described in this databook, was an expansion adapter, which was a jumper to be inserted in a memory chip socket. When a specific address sequence was detected, this jumper would then divert certain bits of the ensuing data to one of the electronic key sockets.
The 1987 Product Data Book of Dallas Semiconductor, which is hereby incorporated by reference, contained more definitive descriptions of the DS1201 Electronic Tag and the DS1204 Electronic Key (now designated as a DS1204U). This data book also described a DS1253 Printer Port keyring. The DS1253 key ring was another expansion adapter, which was a jumper to be inserted into the printer port of a PC, between the computer and its printer. This adapter contained sockets for connection of multiple 5-pin electronic keys (such as the DS1201, the DS1204U, or the then new DS1207, which also contained timekeeping circuitry).
The datasheet for the DS1253 keyring stated that the adaptation would cause no disruption of the interface between computer and printer. Unfortunately, although this scheme worked perfectly well with the standard printer port, many printer and computer manufacturers had inserted nonstandard features to take advantage of the "waste space" in the pin definitions of the standard printer port. In fact, by 1990 so many nonstandard pin definitions have appeared that there is no room for a standard serial interface to be sandwiched in while retaining compatibility with all of the various widespread hardware types.
The 1987-1988 Product Data Book of Dallas Semiconductor, which is hereby incorporated by reference, introduced a preliminary data sheet for yet another electronic key adaptor, the DS1255 Printer Port keyring. The DS1255 keyring was electrically similar to the DS1253 key ring, but was housed in a different physical housing, with a more compact form factor. This housing did not include a ribbon cable (like the DS1250 and DS1253); instead, it provided a single housing with 5-pin keyports on either side.